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Judge Frederick Motz threw out the complaints, citing guidance from recent decisions by appeals courts in the relevant states that prevent "actions brought by indirect purchasers of licences to Microsoft software". Consumers typically buy Windows from indirect resellers such as retail stores.
Antitrust law regarding consumer liability varies from state to state, however. Motz' decision comes after a $1.1bn (£670m) settlement earlier this month in an antitrust suit that called for Microsoft to offer vouchers, ranging in amount from $4 (£2.40) to $29 (£17.60), to California customers of Microsoft software.
Microsoft's legal problems related to private antitrust cases are far from over. Motz recently granted an injunction on behalf of Sun Microsystems, requiring Microsoft to offer Sun's Java to users purchasing Windows.
Microsoft is appealing the decision, but whether or not an appeal is granted, it still faces a court battle in Sun's suit, as well as cases brought by Be, AOL Time Warner and Burst.com.
Other consumer cases in various states are pending.